The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present application.
Isoprene, or 2-methyl-1,3-butadiene with the formula CH2═C(CH3)CH═CH2, is an organic compound naturally produced by many plants. For example, it is a monomer of natural rubber. Under standard conditions, isoprene is a colorless liquid with an aromatic odor. Isoprene is insoluble in water, soluble in alcohol and because of its low boiling point and double bonds, is very reactive.
The polymerization of isoprene using catalysts yields synthetic rubber that closely resembles natural rubber and is used in a wide variety of rubber applications. Examples of synthetic rubber include polyisoprene as well as copolymers styrene-isoprene and butyl rubber. Polyisoprene is used in medical equipment, baby bottle teats/nipples, toys, shoe sole, tires, elastic films and threads for golf balls or textiles, adhesives, paints and coatings. Butyl rubber, made from isobutylene with a small amount of isoprene in the presence of an aluminum chloride initiator, has outstanding impermeability to gases and is used, for example, in inner tubes and tires. Styrene-isoprene rubber is used in pressure sensitive adhesives.
High-purity isoprene is used almost entirely (90-95%) as a monomer in the production of synthetic rubber. Considerably smaller amounts of isoprene are converted as an intermediate into specialty chemicals, including vitamins, pharmaceuticals, flavorings and perfumes, and epoxy hardeners.
Some of the major challenges facing the isoprene market include insufficient supply and increasing prices.
There are several different methods for industrial production of isopropene. The choice of one method over another depends on the availability of the raw materials or feedstock and the economics of the selected process. These processes for producing isopropene are usually developed and routinely used by companies having access to petroleum-based feedstocks. Feedstocks include, for example, tertiary amylenes (dehydrogenation thereof) by Shell, acetylene and acetone by Snamprogetti, isobutylene and formaldehyde by IFP Energies Nouvelles, propylene by Goodyear.
Additionally, isoprene can be recovered from a C5 hydrocarbon mixture or C5 fraction. U.S. Pat. No. 3,510,405 describes a process of purifying isoprene wherein isoprene-containing cyclopentadiene is subject to extractive distillation in the presence of N-alkylated lower fatty acid amide solvent under anhydrous conditions thereby to obtain isoprene as the distillate of the extractive distillation.
U.S. Pat. No. 3,775,259 discloses a process of recovering isoprene from a cyclopentadiene-containing C5 fraction in a two-stage extractive distillation in the presence of a selective polar solvent. During the process, cyclopentadiene is dimerized into dicyclopentadiene at a temperature of 80° C. to 120° C. for easy separation (by distillation) from the solvent.
U.S. Pat. No. 4,647,344 provides a process for recovering isoprene, penta-1,3-diene and cyclopentadiene by liquid-liquid extraction or extractive distillation, wherein the process temperature and the energy consumption can both be kept low.
GB Pat. Nos. 1,072,687, 1,340,149 and 1,417,733 disclose single-, two- and three-stage extraction distillation processes to recover isoprene from C5 hydrocarbon mixtures, respectively.
All aforementioned patents are each incorporated herein by reference in its entirety.
Isoprene must be obtained with a high degree of purity when it is to be used for producing stereospecific polymers because the impurities would be extremely detrimental towards polymerization. In view of the foregoing, new methods of producing isoprene and even new feedstocks for isoprene production are sought to cope with global demand